Occurs when the background operation has completed, has been canceled, or has raised an exception.
Assembly: System (in System.dll)
This event is raised when the DoWork event handler returns.
The Cancelled property of System.ComponentModel.RunWorkerCompletedEventArgs indicates whether a cancellation request was processed by the background operation. If your code in the DoWork event handler detects a cancellation request by checking the CancellationPending flag and setting the Cancel flag of System.ComponentModel.DoWorkEventArgs to true, the Cancelled flag of System.ComponentModel.RunWorkerCompletedEventArgs also will be set to true.
Be aware that your code in the DoWork event handler may finish its work as a cancellation request is being made, and your polling loop may miss CancellationPending being set to true. In this case, the Cancelled flag of System.ComponentModel.RunWorkerCompletedEventArgs in your event handler will not be set to true, even though a cancellation request was made. This situation is called a race condition and is a common concern in multithreaded programming. For more information about multithreading design issues, see Managed Threading Best Practices.
Your AsyncCompletedEventArgs.Error and AsyncCompletedEventArgs.Cancelled properties before accessing the RunWorkerCompletedEventArgs.Result property. If an exception was raised or if the operation was canceled, accessing the RunWorkerCompletedEventArgs.Result property raises an exception.event handler should always check the
The following code example demonstrates the use of the BackgroundWorker class.event to handle the result of an asynchronous operation. This code example is part of a larger example provided for the
' This event handler deals with the results of the ' background operation. Private Sub backgroundWorker1_RunWorkerCompleted( _ ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs) _ Handles backgroundWorker1.RunWorkerCompleted ' First, handle the case where an exception was thrown. If (e.Error IsNot Nothing) Then MessageBox.Show(e.Error.Message) ElseIf e.Cancelled Then ' Next, handle the case where the user canceled the ' operation. ' Note that due to a race condition in ' the DoWork event handler, the Cancelled ' flag may not have been set, even though ' CancelAsync was called. resultLabel.Text = "Canceled" Else ' Finally, handle the case where the operation succeeded. resultLabel.Text = e.Result.ToString() End If ' Enable the UpDown control. Me.numericUpDown1.Enabled = True ' Enable the Start button. startAsyncButton.Enabled = True ' Disable the Cancel button. cancelAsyncButton.Enabled = False End Sub 'backgroundWorker1_RunWorkerCompleted
Available since 10
Available since 2.0
Available since 2.0
Windows Phone Silverlight
Available since 7.0